Loud-speaker unit



April 29, 1930.

M. K. KUCHINSKY LOUD SPEAKER UNIT Filed July 2, 1928 Patented Aer. 29, 1930 narran sraras rasant a asics @ranrv MUD-SPEAKER UNIT Application filed J'uly4 2, 1928. Serial No. 289,984.

This invention relates to driving units for use in connection with` loud speakers, and comprises a device for transforming variable electric currents into mechanical impulses suitable for the actuation of a diaphragm or other similar device for changing these mechanical impulses into sound waves.

It is a general object of the present` invention to provide a novel and improved formvof loud speaker unit.

More particularly one of the features of the invention comprises a novel means of providing for the adjustment of the air gap between the pole faces of the magnet. Another feature consists-in the arrangement of pole pieces to produce a pair of uni directional parallel magnetic fields to cooperate with an armature extending between the fields and provided with means for polarizingthe same, together with unique means for adjusting the lstrength of vone of the paii` of magnetic fields to be equal to that of the other to compensate for the difference in distance of the pole tips from the main poles of the magnet.

Another' feature of the invention comprises a novel mounting for the armature and its flexible support.

A further feature of the invention com- '30 prises the arrangement of a pair of members adapted to be secured to the opposite yedges of the poles of the magnet and to carry the armature supporting means and the armature polarizing means together with novel means for adjusting this assembly to obtain maximum efficiency.

Still another feature of the invention comprises the arrangement of adjusting means between the arms of the horseshoe magnet,

o said means supporting a terminal block and a fulcrum for the multiplying lever.

Other and further features and objectsof the invention will be more apparent to those skilled in the-art upon a consideration of the accompanying drawing and the following specification, wherein is disclosed a single exemplary embodiment ofthe invention with the understanding, however, that various changes may be Amade therein such as fall Within the scope of the appended claims withpair of pole pieces.

out departing from the spirit of the invention..

In said drawings:

Figure 1 is a side elevation of the loud speaker unit showing the same arranged to operate a cone-shaped diaphragm;

Figure@ is a plan view of the same looking at the end of the magnet;

Figure 3 is a vertical section on line 3-3 of Fig. 2;

Figure 4 is a vertical section at right angles to that of Fig. 3 and taken on line H of Fig. 1; and

Figure 5 is a perspective view of the armature and its supporting means.

The present invention contemplates the provision of an'extremely simple loud speaker unit and one which can be assembled-readily for large scale production and, whilebeing cheap to produce, is yet effective in the accurate reproduction of sounds received by it in electrical form. i

The unit as disclosed in the drawings includes the horseshoe or U-shaped magnetV 10 either permanent or electrically excited, having the substantially parallel arms 11, 12, which are rectangular in cross section as best seen in Fig-5.)..` The tips of these arms are cut oi square as shown in the drawing, and' just below the ends have attached to their -inner faces the pole piece supporting blocks 13 of non-magnetic and preferably of insulating material. These blocks are rigidly attached to the inner faces of the arms 11, 12 l by means of screws 14. Since it is desired to provide a pair of unig directional parallel magnetic fields, it is necessary that each arm of the magnet carries a This is contrived by mounting the pole pieces on the upper and i lower surfaces of the pole piece supporting blocks'13, as best shown in Fig. 3. Thus, the lower face of each block 13 has secured thereto a pole 4piece 15, having its rear face 16 tightly abutting against the inner face of the' arm of the magnet. The pole' pieces are formed of blocks of magnetic material of the same width as that of the arms of the magnet. As shown in Fig.2, each tapers to the narrow tip 17 which cooperates with the armature later to be described. They are likewise chamfered on their outer faces as shown at 18 to reduce the area of the actual pole tip to' curing the lower pole pieces and vnumbered 21 passing through closely fitting openings in these pole pieces to insure that they tit with their faces 16 against the magnctarms.`

The screws 22 for the upper pole pieces, however, pass through elongated slots 23 in these pole pieces in order that adjustment may be effected to vary the air gaps 20.

Since an armature is balanced with its opposite ends between the upper pole tips and the lower pole tips and since these ends are equally polarized, it is highly desirable that the magnetic fields at the opposite ends of the armature be of the same intensity. It is well-known that the magnetic field at the very tips' of a U-shaped magnet is more iutense than at any other place. lf. therefore. the pole pieces 15 and 19 were both abutted against the inner faces of the magnet arms, the intensity ot the field between the pole pieces 19 would be greater than that between the pole pieces 15. However, bv providing the adjustable air gaps20, the pole pieceslQ can be adjusted to Aexactly compensate for the greater intensity of magnetic lines at the tin ofthe U-shaped magnet so that a pair of uni# directional parallel magnetic Fields of equal intensity are provided by the present arrangement.

In order to jointly adjust the distance hetween the tips of the two sets of pole pieces to equally change their action ou the armature end, means are provided for drawing together orseparating the arms of the magnet. This means comprises a sleeve 25 of nonmagnetic material internally threaded and secured to the arm 12 by means of the screw 26 passing through that arm. passes through the arm 11 and engages in the threads in the sleeve 25. It is provided with lock nuts 28 and 29 abutting respectively against the inner face of the arm 11 and the outer end of the sleeve 25 so that by proper manipulation of the screw 27 and the lock nuts,v the arms of the horseshoe magnet mayv be drawn together or be separa-ted as desired to adjust the gap between the tips of the pole pieces previously described. j

The armature which is adapted to be balanced between the pole tips comprises a. rectangular block 30 of suitable magnetic material having a length about equal to the vertlcal height between the outer faces of the A screw 27 the armature at right angles to the pla-ne of v the plate. The assembled armature and spring is best shown in Fig. 5.

The ends of the springl plate are each provided with a pair of spaced longitudinal parallel slits 32. and the three tongues thus formed are bent back over the plate as shown in Fig. 5, the center one in one direction and the end Ones in the other to form the curved supporting members 33 and 34. The distance between the ends of the plate as defined by the parts 33 and 34'is slightly greater than the width of the arms '1l and 12 of the magnet. The armature spring plate is attached to the supporting plates 35 best seen in Fig. 1. These plates are of suitable non-magnetic material, and they are arranged to extend over the edges of the arms of the magnet and to be secured against the ends of the nonmagnet blocks 13 by suitable securing means, such as the screws 36, one at each end of each plate. One plate is fastened on either side to the magnet centrally between the upper and lower pole pieces, as shown in Figs. 2v

and 4. Each plate 35 is provided with a lon. gitudinal depression 38 of a. length slightly greater than the. width ot the base of the armature spring plate. and into this depresiol sion, which is curved to conveniently fit the parts 33 and 34, these parts are arranged and suitably secured as by solder as shown at 40. This rigidly and permanently secures the en ds of the spring plate to the supporting plates and insures that, whenl the plates are secured in position by means of the screws 36, the armaturey will be permanently positioned where desired. The position of the armature is adjustable since the openings 37 in the supporting plates through which the screws 36 pass are larger than the screws, allowing the plates 35 `to be slig tly manipulated toexactly centralize the armature between the pole tips both laterally and longitudinally.

The lcoils for polarizing the armature and which are'v excited by the current from a suitably modulated source are connected in series and arranged one'about each end of the armature and in parallel planes. Each coil 42 is in the form of a perforated` flat disk substantially rectangular with rounded corners, asshown best in Figa-2. In reality the coils,are wound on spools of non-conclucting` material. having the cheeks 43 which define the outline of the coil assembly. The thickness of each coil between the outer faces of ly between thevinner face of one set of pole pieces and the projecting ends of the tongues 33 or 34 on the armature spring plate, as

clearly shown in Fig. 4. Thus, each coil is pressed against its corresponding pole pieces and held accurately spaced away from the larmature spring plate. The longer edges of the cheeks of the coils engage the inner f aces of the non-conducting blocks 13 secured to the arms-of the magnet, and the shorter edges of these cheeks engage against the flat inner surfaces of the armature assembly supporting plates 35. The coils are thus rigidly positioned against movement in any direction, and each surrounds one endv of the armat-ure.

In order to provide a rigid terminal block or board to which are secured the leads from the coils, a suitable sheet of insulating ma.- terial, such as libre. is cut to the form shown at 45 and is drilled to be received over the screw 27 on the magnet arm adj lister so that it can he clamped between the end of the sleeve 25 and the lock nut 29 and held in the position best shown in Fig. 4. The termif nals 46 are bolted through this sheet and receive the lugs 47 under the nuts 48. To these lugs are soldered'the ends of the' Wires 49 leading from the coils. This provides a rigid and permanent terminal board which is not subject torattling under violent action of the armature. l

Movement of the armature is adapted to be transmitted to the diaphragm through a link 47 and multiplying lever 48. This lever, which may be of light rigid material, is suitably fulcrumed at one end and at the opposite end 49 is attached to the rod 50 which may be connected to any suitableform of diaphragm, here shown as a cone 51. The lower end of the lever 48 is preferably securedto a thin spring 52 which is drilled to be received over the screw 26 which holds the sleeve 25^in position against the magnet arm 12. A spacer washer fits between the magnet arm and the spring 52 as shown.4 The link 47 is connected at one end to the lug 53 on the upper end of .the armature and 'at the other end by means of a suitable spring or pivot 54 to the lever 48 intermediate its ends.

The device just described is extremely simple to manufacture and is readily -assem bled and adjusted. It is rigid in its construction, insuring against parasitic vibrations and noises, and provides a compact arrangement of an efcient and effective power` unit for driving diaphragms 0f loud speakers.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

l. In a loud speaker, in combination, a magnet having substantially parallel arms, a pair of cooperating pole pieces associated with said arms, a second pair of cooperating polepieces associated with said arms, one pair of pole pieces being in a region of greater iux from said magnet thanthe other,'and means to adjust the flux distribution to equalize it through'the two pairs of pole pieces.

2. In a loud speaker, in combination, -a magnet having a pair of arms with facing surfaces, a :pole piece supporting block secured to each face, a pole piece secured to each block near the ends of the magnet arms, a. pole piece secured to each block at a distance from the ends of said arms and in engagement therewith, each set of pole pieces being adapted to cooperate with one end of a balanced armature, said first set of pole pieces being spaced from said arms, to reduce the flux therethrough to substantially that through the second set.

3. Inl a loudspeaker, in combination, a

magnet having a pair of arms of opposite polarity, two pole pieces for each .arm spaced different distances from the tip thereof, those of the same distance on opposite arms forming cooperating pairs, the pieces of one pair being in closer magnetic relation lto the arms than the other for the purpose described. 4. In a loud speaker, in combination, an armature, an elongated spring extending transverse to and from the center of said ar-4 mature, a coil surrounding' each end of said armature and parallel to lsaid spring, and lugs on the ends of said spring to space said coils therefrom.

5. in a loud speaker, in combination, an armature, an elongated spring extending transverse to and from the center of said armature, the ends of said spring being divided .vith portions thereof turned back over the spring on each side thereof.

6. in a loud speaker, in combination, an armature, an elongated spring extending transverse to and from the center of said. armature, the ends of said spring being divided with portions thereof turned back over the spring on each side thereof, a supporting plate secured to'each end of said spring and a coil surroundingeach end of said armature, each coil engaging both supporting plates and being spaced from said vspring by said turned back ends thereof.

7. In a loud speaker, in combination, an armature, an elongated spring extending transverse to' and from the center of said y turned back ends of said spring, and means securing said ends in said grooves with portions of the turned back ends projecting out of said grooves on each side of the spring.

8. In a loud speaker, in combination, an armature, an elongated -spring extending transverse to and from the center of said ar-I mature, the ends of said spring being divided With portions thereof turned back over the spring on each side thereof, a supporting plate secured to each end of said spring, a coilv surrounding each end of said armature, each coil engaging both supporting plates and being spaced from said spring by said turned` back ends thereof, and pairs of pole pieces cooperating with the ends of said a1'- mature beyond said coils, said pole pieces engaging the outer faces of said coils.

9. In,a loud speaker, in combination. an armature, anv elongated spring extending transverse to and from the center of said armature, the ends of said spring being divided with portions thereof turned back over the spring on each side thereof, a supporting plate secured to each end of said spring, a

, coil surrounding each endl of said armature,

each coil engaging both supporting plates and being spaced from said spring by said turned back ends thereof, pairs of pole pieces cooperating with the ends of said armature beyond said coils, said pole pieces engaging the outer faces of said coils, and means between the pairs of pole pieces engaging the edges of said coils whereby they are prevented from moving in any direction.

10. In a loud speaker, in combination, an armature, an elongated spring extending transverse to and from the center ofsaid armature, the ends of 'said spring being divided with portions thereof turned back over the spring on each side thereof, a supporting plate secured to each end of said spring, a coil surrounding each end of said armature, each coil engaging both supporting plates and being spaced from said spring by said turned back ends thereof, pairsof polepieces cooperating with the ends of said armature beyond said coils` said pole pieces engaging the outer faces. of said coils, and means between the pairs of pole pieces engaging the edges of said coils whereby they are prevented from moving in any direction, the said supporting plates beingv secured to said means.

In testimony whereof I hereunto aiix my signature.

MATTHEW K. KUCHINSKY. 

